Projection of 7 °C increase rejected by climate scientists

National Geographic : A study in Nature that presents the most complete reconstruction so far of 2 million years of global sea-surface temperatures has been both praised and panned by scientists not involved in the work. The scientists say the reconstructed data will play an important role in establishing a clear understanding of Earth’s climate history. But it’s the conclusion that the paper’s author draws—that even if all further greenhouse gas emissions were capped, global temperatures could still rise by up to 7 °C—that has received harsh criticism. The author, Carolyn Snyder, who is now at the US Environmental Protection Agency, says that the prediction was not the primary goal of the work; she was just examining what the relationship between sea-surface temperature and atmospheric carbon dioxide levels might mean in the future. But other scientists argue that she has incorrectly extrapolated the future relationship by basing it on past climate changes that were caused by factors other than greenhouse gases.